Telephone system



PATBNTBD AUG. z5, 1909;

E. G. WEBSTER. TELEPHONE SYSTEM.

APPLIOATION FILED 00119, 1904.

UNITED srnrns Arana rrron.

HARRY G. WEBSTER, OF CHICAGO, ILLINOIS, ASSIGNOR TO MILO G. KELLOGG, OFCHICAGO,

' ILLINOIS.

TELEPHONE SYSTEM.

Original application filed March 27 1903, Serial N o. 149,833.

Specification of Letters Patent.

Serial No. 227,878.

To all whom 'it may concern:

Beit known that I, HARRY G. VnBs'rEn, a citizen of the United States,residing at Chicago, in the county of Cook and State olf Illinois, haveinvented certain new and useful Improvements in Telephone Systems, oli'which the -following is a specilication.

My invention relates to improvements in Vtelephone systems, my objectbeing to provide improved signaling apparatus therein.

In accordance with my invention I provide at the central station asignal controlling electromagnet which is under the control of thesubscriber at the sub-station and is also under the control o'l theoperator at the central station. This electromagnet in the prei'erredform of my invention is preferably a relay magnet which serves tocontrol a signal, such as a lamp.

The signal controlling electromagnet is preferably constructed so thatit is initially controlled by the subscriber at the sub-station, wherebya suitable signal may be actuated to call the attention oi the operatorto the fact that the subscriber desires a connection. The signalcontrolling electromagnet is also adapted to be actuated by theoperator, preferably by the insertion of the connecting plug in a springack or switching terminal of the subscribers line. The initial actuationof the magnet may be utilized to light a lamp as the calling signal, andthe final actuation of the relay which is controlled by the operator maybe utilized 'for rendering the signal inert.

I have illustrated my invention in connection with a signal controllingelectromagnet in the form of a relay having a single armature adapted topartake oi an initial move- 40 ment under the control of the subscriber,and to partake of a iinal movement under the control of the operator,the initial movement serving to actuate the signal for the connection,and the iinal movement serving to render the signal inert; thesemovements may also be utilized -for performing other 'lunctions asdesired.

While I have thus shown the magnet with a single armature adapted topartake of the two distinctive movements, it is apparent that thisselective operation may be procured in other ways, and I do nottherefore desire to limit myself to this particular method ofconstruction.

In its broader phases my invention is described and illustrated in myapplication for United States Letters Patent, Serial blumbei- 149,833,liled March 27th, 1903. In the present application which is a divisionof said prior application I .have illustrated my invention in connectionwith a signal controlling electromagnet in the form of a relay havingtwo energizing windings of different energizing capacities normallydiliferentially connected, and initially responsive to a controlexercised by the subscriber, the circuit through one oi said windings,however, being under the control of the operator whereby a greaterenergization of said relay may be secured.

I have illustrated this application of my invention in the accompanyingdrawings in which Figure l is a diagram illustrating my in vention inconnection with a two wire metallic circuit telephone exchange system 5Fig. 1 a is a detail view showing diagrammat ically the armature andswitching contacts of the relay in their second or intermediate positionFig. 1b is a detail view showing dia- 80 graminatically the armature andswitching contacts of the relay in their third or iina position.

Like letters refer to like parts in the several iigures. 85 Referringiirst to Fig. 1, the subscribers apparatus is represented as consistingof the telephone hook switch c, signal bell o2, condenser t, receiver c,transmitter c7, and induction coil e including the said receiver in itssecondary winding.

Although I have shown but one arrangement it will be understood by thoseskilled in the art that various other 'arrangements of the subscribersapparatus may be used, and I do not confine myself to the particulararrangement illustrated.

Under normal conditions the receiver hangs upon its hook switch, thusclosing the lower contact e a, and maintaining the upper contact o ifopen. The condenser c3 prevents the normal l'low of current from batteryc3 at the central ol'l'ce over the telephone line. l/Vhen, however, thesubscriber removes his telephone from its hook, thus closing the contacte @5 and establishing a relatively low resistance path for the flow ofcurrent through the transmitter c7 and one winding of the repeating coilo, the differentially wound relay c8 at the central oilice will beenergized to alimited extent bythe flow of current from said battery e3,through winding 010, winding c in the opposite direction, through thenormally closed contact between springs d6 and (Z7, over limbs l) a ofthe telephone line, through the normally closed contacts oi the springsdu d10 and d to the ground or common pole of the said battery e3 viaconductor 3. The said energizing winding 07 has a greater number ofturns than `the winding c, or is placed so as to eXert a greaterattractive force upon the armature e', or is otherwise made of greaterenergizing capacity, so as to secure a limited Ienergization of therelay and alimited attraction of its armature c to cause alimitedmovementthereof to close the contact c3 c4, as shown in Fig. l 1. Inorder that the armature c may alter the contacts between the springs dZ7 d8 d d1" and du, it is necessary t at the core of the relay beenergized to a greater extent than can be secured through thc twodi'liierential windings c10 c in series.

rllhe closure of contact c"I c4 established a path for the flow ofcurrent from battery e3 through the signal lamp g, contact c4 c3, overconductor 9, .through the contact between springs d10 and d" and to theother pole ol the said battery. This iiow of current causes theillumination of the said signal lamp g to indicate to the operator thatthe subscriber has removed his telephone from its hook for the purposeof making a call.

Each subscribers line is provided with one or more spring jacks, eachhaving contact pieces connected thereto in a manner similar to the oneindicated in the drawing at aft. Each operator is provided with cordcircuits adapted to unite the lines for conversation similar to the onediagrammatically illustrated. On observing the calling signal theoperator will insert the left hand or answering plug of the cord circuitinto a spring jack of the line corresponding to the calling signal, thuscausing contact pieces h h2 of the said plug to engage respectively withthe contact pieces a t of the spring jack. The contact pieces h2 tcomplete a new circuit for the flow of current from battery e3 throughwinding 01, contact b h2, cord strand Z, relay o to the ground or commonpole of the said battery e3. This iiow of current causes the operationof the said relay o and also causes the complete energization of therelay 08. The winding C10 now has la flow of current through itmaterially greater than the flow of current through the winding c, andhaving a greater energizing capacity than said latter winding, causesthe complete attraction of the armature c to alter the contacts betweenthe springs d, Z7 d8 dg d10 and d as follows Contact between springs d10and d is broken to interrupt the iiow of current through the signal lampg; contact between springs du and d10 is broken to disconnect the linecircuit from the local signaling circuit, contact between springs d and(Z7 is broken to interrupt the flow of current through winding c, andcontact between springs d7 and Z8 is established to connect the testcontact b of the jack directly to the limb b of the line without theintervention of the winding c". As a result of the complete operation ofthe said relay e8 the line signal gis eilaced, the normal connections tothe line circuit are destroyed and the said line circuit is connecteddirectly to the cord circuit without intervening electromagnets ordirect ground. connections.

The energization oi' relay o/ causes the attraction of its armature 0^Land would cause the illumination of the supervisory lamp oG were thesubscribers telephone not removed from its hook. rlhe telephone beingoil its hook, however, a iiow of current is established through therelay 0 as follows t-from battery e3 through winding 610 contact betweensprings d7 d8, limbs l) and a of the telephone line, over cord strand7C, through relay 0 to the ground or common side of the said battery e3.Relay 0 is thus energized, attracts its armature 02, and opens thecircuit through the supervisory lamp o at the normally closed contact o307. The said supervisor-y lamp 0U is thus prevented from giving itssignal at this time.

Condensers m m are interposed in the strands of the cord circuit toallow the operator to converse with the calling subscriber at this timeand to allow conversation be- 100 tween the two subscribers when theconnection has been completely established. The operator depresses thelistening-in keys n n, thus cutting her telephone s into theconversational circuit, and having determined from 105 the callingsubscriber the number oi the subscriber desired, touches the tip contactpiece i of the right hand plug to the test ring t of a spring jack oithe line wanted. lf the line be busy the said contact 1) will have apoten- 110 tial different from that of the battery e3 and a flow ofcurrent will result from the said battery e, .over conductor 10, throughthe tertiary winding S5 of the operators induction coil, contact n2 n oithe operators listening- 115 in key, over cord strand k, through the tipcontact i of the plug and testing contact t of the spring jack of theline tested, where it unites with the current flowing from the batterye3 through the winding 01 of the busy 120 line. This flow of Vcurrentthrough the tertiary winding S5 will produce a ilow of current throughthe circuit including the operators telephone s causing a click therein.The operator upon hearing the busy click 125 will advise the callingparty that the desired subscriber is busy. Should, however, the desiredline be idle the testing terminals b of all spring jacks connected withthe desired subscribers line would be at the same poten- 130 tial as thebattery e3 and the testing contact i of the plug, and no flow of currentwould result through the said tertiary winding S5 when the test wasmade. The operator would thus hear no click, would know that the desiredline was idle, would insert the right hand plug into the spring jack ofthe desired line, and depress the ringing keys t t to include in circuitwith the calling bell @2 at the subscribers station, the callinggenerator t2, thus causing the desired subscribers bell to ring. At thistime the relay es associated with the desired subscribers line ismaintained in an operated position by a current flowing from battery ethrough winding c1, jack and plug contact l2 t2, cord strand Z, throughcontact t t3 to the ground pole of said battery c3. This flow of currentthrough the winding ci is sufficient to cause the complete energizationof the said relay C8 and the complete attraction of its armature c justas described with reference to the calling subscribers line. A path forthe ringing current is thus established directly over the limbs a and l)of the subscriber-s line, the said current returning to the groundpoleof the said generator through contact t t3. The subscribers bell isthus caused to ring and notify the subscriber that his attention isdesired. Before the said subscriber responds to his call a path for thefiow of current is provided from battery e3 through winding el of therelay associated with the called for subscribers line, jack and plugcontact b i2, cord strand Z, relay p and to the groundpole of saidbattery e3. This flow of current causes the operation of both relay pand CS, just as described with reference to the calling subscribersline. The complete energization and operation of the said relay 08prevents the illumination of the line signal g, while the operation ofrelay p closes .the contact p p5 and causes the illumination of thesupervisory lamp p lto indicate to the operator that the called-forsubscriber has not as yet responded. No path for the flow of currentthrough relay p exists at this time. As soon, however, as the called-forsubscriber removes his telephone from its hook a new path for the flowof current from battery e3 is provided through winding 010, limbs l) anda of the telephone line, through the said relay'p and to the ground orcommon side of the said battery e3. Relay p is thus energized, attractsits armature p2 and opens the circuit through supervisory lamp p tocause its extinction and to notify the operator of the response of thecalled-for subscriber.

Both subscribers are now in conversation with each other through thecord strands lc l and condensers m m, their transmitters being energizedby current from battery e3 through the windings cw of the relays e8, thecurrent returning through the relays 0 and p. The relays 0 and p are ofrelatively low resistance compared with the resistance of the relays 0p', thus securing a sufficient flow of current over the telephone linesfrom battery e3 to satisfactorily energize the transmitters. As soon aseither subscriber replaces his telephone upon his hook the correspondingre'- lay p or 0 is denergized, thus causing the illumination ol thecorresponding supervisory signal p6 or 0b'. When both subscribersreplace their telephones upon their hooks both of' said supervisorysignals will be illuminated, thus indicating to the operator thatdisconnection is desired. Upon withdrawing the plugs from the springjacks the relays and associated apparatus will return to their normalpositions indicated in Fig. 1.

Recapitulating, the energizing winding c10 is made of sullicientlyhigher energizing capacity than the energizing winding 0') to cause alimited energization only of the relay C8 when the same currenttraverses both of said windings. This limited energization of the saidrelay causes a partial attraction of its armature, or a limited movementof its associated signaling mechanism, to cause the appearance of thecalling signal to indicate to the operator that a connection is desired.When, however, the cord circuit is connected -with the line circuit,either in response to a call or for the purpose of making connectionwith the called-for subscribers line, a circuit is established throughone of said energizing windings only to cause the complete attraction ofthe relay armature, or the further movement oi the associated signalingmechanism, to efface the calling signal and to destroy the normalnon-inductive path for the flow of current to ground from theconversational circuit thus established and to remove the inductivewindings from said circuit.

It is apparent that many alterations and modifications will occur tothose skilled in the art for securing a sufficient difference betweenthev energization of the relay c8 when windings 010 and c are in circuitand when winding c1 is alone in circuit with the cord connectingapparatus, whereby the relay magnet may control two definite movementsof its associated switching apparatus.

It will also be obvious to those skilled in the art that my invention isnot confined t0 its application in a switch board system of thecharacter illustrated in the accompanying drawings, but that it may beapplied to and utilized in other telephone exchange systems, and insignaling systems in general.

I have found that a sufficient difference between the energizingcapacities of the two windings C10 e9 may be secured in practice bymaking winding C10 of 200 ohms and winding c9 of 175 ohms of the samesize of wire,`properly disposed upon the core, but other proportionsbetween the two windings may be Aadvantageously used depending upon theresistance of the other associated parts.

I claim:

l. ln a telephone exchange system, a central O'Hice and a subscribersline circuit, a source of current for the line, means at the subscribersstation to determine the current 'flow in the line, a combined signaland' cut-orf magnet connected in the line and adapted to control its owncircuit connections and controlled by the current in the line asdetermined by the subscriber lor exhibiting a signal, together withoperators connective apparatus having means becoming operative in theuse of the apparatus to produce an increase of the current flow in thewindings of' said signal and cut-off magnet to further energizeV thesame and operate the cut-off, thereby removing itself from thepossibility of line control as long as a connection continues.

2. ln a telephone exchange system, a central station and a subscribersstation and a source of current supply with the subscribers linenormally connected thereto, a combined signal and eut-off magnet havingtwo windings normally included in the line and in series with saidsource oi' current, an armature for said magnet adapted to set a signalin response to current 'flow in one winding of the magnet, as determinedby the subscriber, together with means controlled in making connectionwith the line to produce an increased current 'flow in the other windingwhereby the armature will sever the connection of the iirst winding ofthe line.

3. In a telephone exchange system, a subscribers line circuit, asubscribers station and a central station, and a source of current atthe latter for supplying the line as determined. by the subscriber, asignal magnet having its winding normally included serially in the linewith said source, an armature for said magnet with a signal device and aline cut-oil device controlled by the armature, means whereby the actionof the armature in response to normal signaling current in the line islimited to setting a signal, and further means under the control of anoperator to produce an increased current flow through a portion of themagnet winding whereby the armature will operate the cut-off device toremove the magnet from its serial connection with the line and to retirethe signal.

4. In a telephone exchange system, a subscribers line circuit, asubscribers station and a central station, and a source of current atthe latter for supplying the line as determined by the subscriber, asignal magnet having its winding normally included serially in the linewith said source, an armature for said magnet with a signal device andaline cut-off device controlled by the armature, means whereby theaction of the armature in response to normal signaling current in theline is limited to setting a signal, and further means under the controlof an operator to close a local circuit through the source of currentand a portion of the magnet winding to produce an increased. flow andincreased energization of the magnet, whereby the armature will actfurther to break the connection of the magnet to line, and will retirethe signal.

5. In a telephone exchange system, a central station and a subscribersstation and a metallic circuit interconnecting them, a source of currentand means at the subscribers station to determine the flow therefrom inthe line, a signal controlling magnet for the line at the central oflicehaving its windings included serially in the line with an includedcut-olf device, an armature for the magnet adapted to be moved in twosteps, the lirst step in response to line current to set the linesignal, and the second step to worl; the cut-off device, connectionterminals for the line, and means controlled by an operator in the useoi said connection terminals to close a local circuit through a portionof the magnet winding to move the armature its second step and therebyto sever the line connection of the magnet winding and retire thesignal.

6. ln a telephone exchange system, a metallic line circuit, and a relayhaving its windings normally connected thereto through closed cut-offcontacts, a local signal circuit connected to normally open contacts ofsaid relay, means to limit the eiective energization of the relay magnetby line current so that its armature will close the local signal circuitonly, and means under the control of an operator to increase theeffective energization of the magnet so that its armature will actfurther to open the cut-ofi contacts and sever the line connection tothe relay.

7. ln a telephone exchange system, a substation and. a central stationwith a line circuit interconnecting them, means at the substation todetermine the flow of current in the line, a combined signal and cut-oilrelay for the line at central having two windings normally includedserially in the line with cut-off contacts normally closed, an armaturefor said relay adapted to control a normally open signal circuit andthereafter when actuated further to open the said cutoil contacts,connection terminals for the line and cord circuits cooperatingtherewith, a-sourcc oi' current and a pair oi' bridged relays in eachcord circuit, a supervisory signal jointly controlled by said bridgedrelays, one relay adapted to be included in a local circuit to close thesupervisory signal circuit when connection is made with the line, andthe other relay to control the said signal circuit in response tocurrent over the line circuit, together with means whereby current inthe line circuit as determined by a call from the substation willattract the relay armature to close the normally open line signalcircuit but will not open the cut-oil contacts, and trolled by saidelectro-magnet and adapted,

means actuated by an operator in responding to the call to include onewinding or the line relay in the local circuit with the firstsupervisory relay, whereby the line relay is out oiic from line and thesupervisory signal circuit is simultaneously closed.

S. ln a telephone exchange system, the combination with a telephone lineconnecting a sub-station with a switching terminal at the centralo'l'lice, a switch at the substation controlling the flow of currentover the said telephone line through the substation, a cord circuit atthe central o'l'lice adapted to make connection with the said switchingterminal and to complete a circuit therethrough over said telephoneline, a signal receiving electro-magnet, having two differentiallyconnected energizing windings of diliierent energizing capacitiesnormally included in circuit with said telephone line and with asuitable source of current, and normally responsive to currents oversaid line controlled by the sub-station switch, associated signalingmechanism controlled by said electro-magnet and adapted, under thelimited energization thereof controlled by said sub-station switch, tocause the display of its signal, means for energizing saidelectro-magnet to a greater extent over a circuit established throughone of said energizing windings when the cord circuit is connected tothe line whereby the said signaling mechanism is caused to otlace thesaid signal, means whereby the operator may determine the idle or busycondition of a tested line, a signal controlling electromagnetassociated with said cord circuit and under the control of thesub-station switch when the telephone line is switched for conversation,a second signal controlling electro-magnet associated with said cordcircuit and energized over the circuit established by the connection ofthe cord circuit to the telephone line, and a supervisory signal jointlycontrolled by the said two electro-magnets.

9. In a telephone exchange system, the combination with a telephone lineconnecting a sub-station with a switching terminal at the centraloilicc, a switch at the substation controlling the flow of current overthe said telephone line through the substation, a cord circuit at thecentral o'Hice adapted to make connection with the said switchingterminal and to complete a circuit theiethrough over said telephoneline, a signal receiving electro-magnet, having two differentiallyconnected energizing windings of di'fl'erent energizing capacitiesnormally included in circuit with said telephone line and with asuitable source of current, and normally responsive to currents oversaid line controlled by the sub-station switch, associated signalingmechanism conunder the limited energization thereof con- Y trolled bysaid sub-station switch, to cause the display of its signal, means forenergizing said electro-magnet to a greater extent over a circuitestablished through one of said energizing windings when the cordcircuit is connected to the line whereby the said signaling mechanism iscaused to efface the said signal, means whereby the operator maydetermine the idle or busy condition of a tested line, and a signalcontrolling electro-magnet associated with said cord circuit and underthe control of the substation switch when the telephone line is switchedfor conversation.

l0. In a telephone exchange system, the combination with a telephoneline connecting a sub-station with a switching terminal at the centraloilice, a switch at the substation controlling the low of current overthe said telephone line through the substation, a cord circuit at thecentral office adapted to make connection with the said switchingterminal and to complete a circuit therethrough over said telephoneline, a signal receiving electro-magnet, having two di'li'erentiallyconnected energizing windings of dii'lerent energizing capacitiesnormally included in circuit with'said telephone line and with asuitable source of current, and normally responsive to currents oversaid line controlled by the sub station switch, associated signalingmechanism controlled by said electro-magnet and adapted, under thelimited energization thereof controlled by said sub-station switch, tocause the display of its signal, means for energizing saidelectro-magnet to a greater extent over a circuit established throughone of said energizing windings when the cord circuit is connected tothe line whereby the said signaling mechanism is caused to efface thesaid signal, a signal controlling electromagnet associated with saidcord circuit and under the control of the sub-station switch when thetelephone line is switched for conversation, a second signal controllingelectromagnet associated with said cord circuit and energized over thecircuit established by the connection of the cord circuit to thetelephone line, and a supervisory signal jointly controlled by the saidtwo electro-magnets.

11. In a telephone exchange system, the combination with a telephoneline connecting a sub-station with a switching terminal at the centraloHice, a switch at the sub-station controlling the ilow of current overthe said telephone line through the sub-station, a cord circuit at thecentral ollice adapted to make connection with the said switchingterminal and to complete a circuit therethrough over said telephoneline, a signal receiving electro-magnet, having two differentiallyconnected energizing windings of different energizing capacitiesnormally included in circuit with said telephone line and lcontrolled bythe sub-station switch, associated signaling mechanism controlled bysaid electro-magnet and adapted, under the limited energization thereofcontrolled by said sub-station switch, to cause the display of itssignal, means for energizing said electromagnet to a greater extent overa .circuit established through one of said energizing windings when thecord circuit is connected to the line whereby the said signalingmechanism is caused to efface the said signal, and a signal controllingelectro-inagnet associated with said cord circuit and under the controlof the sub-station switch when the telephone line is switched forconversation.

l2, In a telephone exchange system, the combination with a telephoneline connecting a sub-station with a switching terminal at the centraloffice, a switch at the sub-station controlling the flow of current overthe said telephone line through the sub-station, a cord circuit at thecentral oflice adapted to make connection with the said switching tei'-mina'l and to complete a circuit therethrough over said telephone line,a signal receiving electro-magnet', having two differentially connectingenergizing windings of different energizing capacities normally includedin circuit with said telephone line and with a suitable source ofcurrent, and normally iesponsive to currents over said line controlledby the sub-station switch, associated. signaling mechanism controlled bysaid electromagnet and adapted, uiiderthe limited. energization thereofcontrolled by said sub-station switch, to cause the display of itssignal, means for energizing said electro-magnet to a greater extentover a circuit established through one of said energizing windingsv whenthe cord circuit is connected to the line wheieby the said signalingmechanism is caused to efface the said signal and means whereby theoperator may determine the idle or busy condition of a tested line.

13. In a telephone exchange system, the combination with a telephoneline connecting a sub-station with a switching terminal at the centraloffice, ya switch at the sub-station controlling the flow ofcurrent overthe said telephone line through the sub-station, a cord circuit at thecentral office adapted to make connection with the said switchingterminal and to complete a circuit therethrough over said telephoneline, a signal receiving electromagnet, having two differentiallyconnected energizing windings of different energizing capacitiesnormally included in circuit with said telephone line and with asuitable source of current, and normally responsive to currents oversaid line controlled by the substation switch, associated signalingmechanism controlled by said electro-magnet and adapted, under thelimited energization thereof controlled by said sub-station switch, tocause the display of its signal and means for energizing saidelectro-magnet to a greater extent over a circuit established throughone of said energizing windings when the cord circuit is connected tothe line whereby the said signaling mechanism is caused to efface thesaid signal.

14; In a telephone exchange system, the combination with a telephoneline connecting a sub-station with the central office and provided witha switching terminal thereat, a signal receiving electro-magnetassociated with said line and having two differentially connectedenergizing windings of different energizing capacities normally inncircuit therewith adapted to energize said electromagnet to a limitedextent only to cause the display of its signal when the line circuit isclosed at the sub-station, cord connecting apparatus adapted to makeconnection with the said switching terminal and establish a new path forthe greater flow of current through one of said energizing windings tocause a greater energization of said electromagnet whereby the saidsignal is again eifaced when the said line is switched for conversation,switching mechanism also controlled by said. electro-inagnet adapted toremove the impedance of its other energizing winding from the circuitextending between the sub-station and the said switching terminal whenthe line is switched for conversation, means whereby the operatormaydetermine the idle or busy condition of a tested line, a signalcontrolling electro-magnet associated with said cord connectingapparatus and under the control of the sub-station switch when thetelephone line is switched for conversation', a second signalcontrolling electro-magnet associated with said cord connectingapparatus and energized over the said circuit established by theconnection of the cord circuit to the telephone line, and a supervisorysignal jointly controlled by the said two electro-magnets.

15, In a telephone exchange system, the combination with a telephoneline connecting a sub-station with the central office and provided witha switching terminal thereat, a signal receiving electro-inagnetassociated with said line and having two differentially connectedenergizing windings of dierent energizing capacities normally in circuittherewith adaptedto energize said electromagnet to a limited extent onlyto cause the display of its signal when the line circuit is closed atthe sub-station, cord connecting apparatus adapted to make connectionwith the said switching terminal and establish a new path for thegreater flow of current through one of said energizing windings to causea greater energization of said electro- L@ remove the impedance of itsother energizing winding from the circuit extending between thesub-station and the said switching terminal when the line is switchedfor conversation, means whereby the operator may determine the idle orbusy condition of a tested line, and a signal controlling electro-magnetassociated with said cord connecting apparatus and under the control ofthe sub-station switch when the telephone line is switched forconversation.

16. In a telephone exchange system, the combination with a telephoneline connecting a sub-station with the central oliice and provided witha switching terminal thereat, a signal receiving electro-magnetassociated with said line and having two differentially connectedenergizing windings of different energizing capacities normally incircuit therewith adapted to energize said electromagnet to a limitedextent only to cause the display of its signal when the line circuit isclosed at the sub-station, cord connecting apparatus adapted to makeconnection with the said switching terminal and establish a new path forthe greater iiow of current through one of said energizing windings tocause a greater energization of said electromagnet whereby the saidsignal is again effaced when the said line is switched for conversation,switching mechanism also controlled by said electro-magnet adapted toremove the impedance of its other energizing winding from the circuitextending between the sub-station and the said switching terminal whenthe line is switched for conversation and a signal controllingelectro-magnet associated with said cord connecting appa- -ratus andunder the control oi' the sub-station switch when the telephone line isswitched for conversation.

17. In a telephone exchange system, the combination with a telephoneline connecting a sub-station with the central office and provided witha switching terminal thereat, a signal receiving electro-magnetassociated with said line and having two differentially connectedenergizing windings of different energizing capacities normally incircuit therewith adapted to energize said electromagnet to a limitedextent only to cause the display of its signal when the line circuit isclosed at the sub-station, cord connecting apparatus adapted to makeconnection with the said switching terminal and establish a new path forthe greater' low of current through one of said energizing windings tocause a greater energization of said electro-magnet whereby the saidsignal is again ei'iaced when the said line is switched forconversation, and switching mechanism also controlled by saidelectro-magnet adapted to remove the impedance of its other energizingwinding from the circuit extending between the sub-station and the saidswitching terminal when the line is switched for conversation.

18. In a telephone exchange system, the combination with a telephoneline connecting the sub-station with the central oiiice and providedwith a switching terminal thereat, a signal receiving electro-magnetassociated with said line and having two differentially connectedenergizing windings of different energizing capacities normally incircuit therewith adapted to energize said electromagnet to a limitedextent only to cause the display of its signal when the line circuit isclosed at the sub-station, cord connecting l apparatus adapted to makeconnection with the said switching terminal and to establish a new pathfor the flow of current through one of said energizing windings only tocause a greater' energization of said magnet whereby the said signal isagain eiiaced when the said line is switched for conversation andswitching mechanism also controlled by said electro-magnet adapted to-remove the impedance of its other energizing winding from the circuitextending between the sub-station and the'said switching terminal whenthe line is switched for conversation.

19. ln a telephone exchange system, the combination with a telephoneline connecting a sub-station with the central olice and provided with aswitching terminal thereat, a signal receiving electro-magnet associatedwith said line "and having two differentially connected energizingwindings of different energizing capacities normally in circuittherewith adapted to energize said. electromagnet to a limited extentonly to cause the display of its signal when the line circuit is closedat the sub-station, cord connecting apparatus adapted to make connectionwith the said switching terminal and to establish a new path for theflow of current through one of said energizing windings only to cause agreater energization of said magnet whereby the said signal is againefiaced when the said line is switched for conversation, switchingmechanism also controlled by said electro-magnet adapted to remove theimpedance of its other energizing winding from the circuit extendingbetween the sub-station and the said switching terminal when the line isswitched for conversation, and means whereby the operator may determinethe idle or busy conditionv of a tested line.

20. In a telephone exchange system, the combination with a telephoneline connecting a sub-station with the central office and provided witha switching terminal thereat, a signal receiving electro-magnetassociated with said line and having two differentially connectedenergizing windings of different energizing capacities normally incircuit therewith adapted to energize said electromagnet to a limitedextent only to cause the display of its signal when the line circuit isclosed atthe sub-station, cord connecting apparatus adapted to makevconnection with the said switching terminal and to establish a new pathfor the flow of current through one of said energizing windings only tocausev .the line is switched for conversation, and a signal controllingelectro-magnet associated with said cord connecting apparatus and underthe control of the sub-station switch when the telephone line isswitched for conversation.

21. ln a telephone exchange system, the combination with a telephoneline connecting a sub-station with the central ofiice and providedA witha switching terminal thereat, a signal receiving electro-magnetassociated with said line and having two differentially connectedenergizing windings` of different energizing capacities normally incircuit therewith adapted to energize said electromagnet to a limitedextent only to cause the display of its signal when the line circuit isclosed at the sub-station, and cord connecting apparatus adapted to makeconnection with the said switching terminal and establish a new path forthe greater flow of current through one of said energizing windings tocause a greater energization of said electromagnet whereby the saidsignal is again effaced when the said line is switched for conversation.

22. In a telephone exchange system, the combination with 'a telephoneline connecting a sub-station with the central office and provided witha switching terminal thereat, a signal receiving electro-magnetassociated with said line and having two differentially connectedenergizing windings of different venergizing capacities normally incircuit therewith adapted to energize said electromagnet to a limitedextent only to cause the display of its signal when the line circuit isclosed at the sub-station, and cord connecting apparatus adapted to makeconnection with the said switching terminal and to establish a newpath'for the flow of current through one of said energizing windingsonly to cause a greater energization of said magnet whereby the saidsignal is again effaced when the said line is switched for conversation.

y 23. In a telephone exchange system, the combination with a telephoneline connecting the sub-station with the central office and providedwith a switching terminal thereat, a signal receiving electro-magnetassociated with said line and having two differentially connectedenergizing windings of different energizing capacities normally incircuit therewith adapted to energize said electromagnet to a limitedextent only to cause the display of its signal when the line circuit isclosed at the sub-station, cord connecting apparatus adapted to makeconnection with the said switching terminal and establish a new path forthe greater flow ofl current through one of said energizing windings tocause a greater energizationof said electromagnet whereby the saidsignal is again effaced when the said line is switched for conversation,and means whereby the operator may determine the idle or busy conditionof a tested line.

24. In a telephone exchange system, the combination with a telephoneline connecting a sub-station with the central office and provided witha switching terminal thereat, a signal receiving electro-magnetassociated with said line and having two differentially connectedenergizing windings of different energizing capacities normally incircuit therewith adapted to energize said electromagnet to a limitedextent only to cause the display of its signal when the line circuit isclosed at the sub-station, cord connecting apparatus adapted to makeconnection with new path for the greater flow of current through one ofsaid energizing windings to cause a greater energization of' saidelectromagnet whereby the said signal is again effaced when the saidline is switched for conversation, and a signal controllingelectromagnet associated with said cord connecting apparatus and underthe control ofl the substation switch when the telephone line isswitched for conversation.

25. In a telephone exchange system, the combination with a telephoneline connecting the sub-station with the central office and providedwith a switching terminal thereat, a signal receiving electro-magnetassociated with said line and having two differentially connectedenergizing windings of different energizing capacities normally incircuit therewith adapted to energize said electro-magnet to a limitedextent only to cause the display the sub-station, cord connectingapparatus adapted to make connection with the said switching terminaland establish a new path for the greater ilow of current through one ofsaid energizing windings to cause a greater energization of saidelectro-magnet whereby the said signal is again eflaced when the saidline is switched for conversation, means whereby the operator maydetermine the idle or busy condition of a tested line, and a the saidswitching terminal and establish a of its signal when the line circuitis closed at SQI signal controlling electro-magnet associated with saidcord connecting apparatus and under the control of the sub-stationswitch when the telephone line is switched for convel-sation.

26. In a telephone exchange system, the combination with a telephoneline connecting a sub-station with the central oflice and provided witha switching` terminal ther-cat, a signal receiving electro-magnetassociated with said line and having two differentially connectedenergizing windings or' different energizing capacities normally incircuit therewith adapted to energize said electro-magnet to a limitedextent only to cause the display of its signal when the line circuit isclosed at the sub-station, cord connecting apparatus adapted to makeconnection with the said switching terminal and establish a new path forthe greater flow of current through one of said energizing windings tocause a greater energization of said electromagnet whereby the saidsignal is again elfaced when the said line is switched for conversation,means whereby the operator may determine the idle or busy condition of atested line, a signal controlling electro-magnet associated withsaid-cord connecting apparatus and under the control of the sub-stationswitch when the telephone line is switched for conversation, a secondsignal controlling electro-magnet associated with said cord connectingapparatus and energized over the said circuit established by theconnection of the cord circuit to the telephone line, and a supervisorysignal jointly controlled by the said two electro-magnets.

27. In a telephone exchange system, the combination with a telephoneline connecting a sub-station with the central oHice, a cord circuit atthe central office for making connection with the said line, a signalreceiving electro-magnet associated with said line, having twodifferentially connected windings of different energizing capacities, aconnection to a source of current extending from one side or' said lineadapted to complete the circuit through both of said windings when thecircuit is closed at the sub-station to cause a limited energizationonly of said electro-magnet whereby the display of its signal ise'li'ected, switching contacts adapted, when the line is connected withthe cord. circuit, to cause a greater flow of current through one ofsaid energizing windings whereby a greater energization of saidelectro-magnet is caused lto efface said signal, switching mechanismcontrolled by said electro-magnet adapted to remove tlre impedance ofits other energizing winding from the circuit extending between thesub-station and the said switching terminal when the line is switchedfor conversation, means whereby the operator may determine the idle orbusy condition of a tested line, a signal controlling electro-magnetassociated with said cord circuit and under the control of thesub-station switch when the telephone line is switched for conversation,a second signal controlling electro-magnet associated with said cordcircuit and energized over the circuit established by the connection ofthe cord circuit to the telephone line, and a supervisory signal jointlycontrolled by the said two electro-magnets.

2S. In a telephone exchange system, the combination with a telephoneline connecting a sub-station with the central office, a cord circuit atthe central oflice for making connection with the said line, a signalreceiving electro-magnet associated with said line, having twodifferentially connected windings of diilerent energizing capacities, aconnection to a source of current extending from one side of said lineadapted to complete the circuit through both of said windings when thecircuit is closed at the sub-stationA to cause a limited energizationonly of said electro-magnet whereby the display of its signal iseffected, switching contacts adapted, when the line is connected withthe cord circuit, to cause a greater flow of current through one of saidenergizing windings whereby a greater energization of saidelectro-magnet is caused to efface said signal, switching mechanismcontrolled by said electro-magnet adapted to remove the impedance of itsother energizing winding from the circuit extending between thesub-station and the switching terminal when the line is switched `forconversation, means whereby the operator may determine the idle or busycondition of a tested line, and a signal controlling electro-magnetassociated with said cord circuit and under the control of thesubstation switch when the telephone line is switched for conversation.

29. 1n a telephone exchange system, the combination with a telephoneline connecting a sub-station with the central oflice, a cord circuit atthe central oilice for making connection with the said line, a signalreceiving electro -magnet associated with said line having twodii'lerentially connected windings of diii'erent energizing capacities,a connection to a source or' current extending from one side of saidline adapted to complete the circuit through both of said windings whenthe circuitis closed at the sub-station to cause a limitedI energizationonly of said electromagnet whereby the display of its signal iseiiected, switching contacts adapted, when the line is connected withthe cord circuit, to cause a greater 'flow of current through one ofsaid energizing windings whereby a greater energization of saidelectro-magnet is caused to eilaee said signal, switching mechanismcontrolled by said electro-magnet adapted to remove the impedance of itsother energizing winding from the circuit extending between thesub-station and the said switching terminal when the line is switchedfor conversation, and a signal controlling electro-magnet associatedwith said cord circuit and under the control of the sub-station switchwhen the telephone line is switched for conversation.

electro-magnet whereby 'the display of itssignal is effected, switchingcontacts adapted, when the line is connected with the cord circuit, tocause a greater flow of current through one of said energizing windingswhereby a greater energization of said electro-magnet is caused toefface said signal, and switching mechanism controlled by saidelectro-magnet adapted to remove the impedance of its other energizingwinding from the circuit extending between the sub-station and the saidswitching terminal when the line is switched for conversation.

31. In a telephone exchange system, the combination with a telephoneline connecting a sub-station with the central office, a cord circuit atthe central office for making connection with the said line, a signalreceiving electro-magnet associated with said line having twodifferentially connected windings of differentl energizing capacities, aconnection to a source of current extending from one side of said lineadapted to complete the lcircuit through both of said windings when thecircuit is closed at the sub-station to cause a limited energizationonly of said electromagnet whereby the display of its signal iseffected, switching contacts adapted, when the line is connected withthe cord circuit, to cause a fiow of current through one of saidenergizing windings without also passingl through the other energizingwinding, whereby a greater energization of said electromagnet is causedto efface said signal, and switching mechanism controlled by saidelectro-magnet adapted to remove the impedance of its said otherenergizing winding fromv the circuit extending between the substationand the said switching terminal when the line is switched forconversation.l

32. In a telephone exchange system, the combination with a telephoneline connecting a sub-station with the central office, a cord circuit atthe central office for making connection with the said line, a signalreceiving electro-magnetl associated with said line having twodifferentially connected windings of different energizing capacities, aconnection to a source of current extending from one side of said lineadapted to complete the-circuit through both of' said windings when thecircuit is closed at the sub-station to cause a limited energizationonly of said electromagnet whereby the display of its signal iseffected, switching contacts adapted, whenV the line is connected withthe cord circuit, to cause a flow of current through one of saidenergizing windings without also passing through the other energizingwinding, whereby a greater energization of said electro-magnet is causedto efface said signal, switching mechanism controlled by saidelectro-magnet adapted to remove the impedance of its said otherenergizing winding from` the circuit extending between the sub-stationand the said switching terminal when the line is switched forconversation, and means whereby the operator may determine the idle orbusy condition of a tested line.

38. In a telephone exchange system, the combination with a telephoneline connecting a sub-station with the central office, a cord circuit atthe central office for making connection with the said line,A a signalreceiving electro-magnet associated with said line having twodifferentially connected windings of different energizing capacities, aconnection to a source of' current extending from one side of said lineadapted to complete the circuit through both of said windings when thecircuit is closed at the sub-station to cause a limited energizationonly of said electro-magnet whereby the display of' its signal iseffected, switching contacts adapted, when the line is connected withthe cord circuit, -to cause a flow of current through one of saidenergizing windings without also passing through the other energizingwinding, whereby a greater energization of' said electro-magnet iscaused to efface said signal, switching mechanism controlled by saidelectro-magnet adapted to remove the impedance of its said otherenergizing winding from the circuit extending between the sub-stationand the said switching terminal when the line is switched forconversation, and a signal controlling electro-magnet associated withsaid cord circuit and under the control of the substation switch whenthe telephone line is switched for conversation.

34. ln a telephone exchange system, the combination with a telephoneline connecting a sub-station with the central office, a cord circuit atthe central office for making cony nection with the said line, a signalreceiving electro-magnet associated with said line having twodifferentially connected windings of different energizing capacities, aconnection to a source of current extending from one side of said lineadapted to complete the circuit through both of' said windings when thecircuit is closed at the sub-station to cause a limited energizationonly of said electro-magnet whereby the display of its signal iseffected, and switching contacts adapted, when the line is connectedwith the cord circuit, to cause a flow of current through one of saidenergizing windings whereby a greater energization of saidelectro-magnet is caused to efface said signal` 35. In a telephoneexchange system, the combination with a telephone line connecting asub-station with the central office, a cord circuit at the central olicefor making connection with the said line, a signal receivingelectro-magnet associated with said line having two differentiallyconnected windings of different energizing capacities, a connection to asource of current extending from one side of' said line adapted tocomplete the circuit through both of said windings when the circuit isclosed at the sub-station to cause a limited energization only of saidelectro-inagnet whereby the display of its signal is effected, andswitch contacts adapted, when the line is connected with the cordcircuit, to cause a greater flow of current through one of saidenergizing windings without also passing through the other energizingwinding, whereby a greater energization of said electro-magnet is causedto eiface said signal.

36. In a telephone exchange system, the combination with a telephoneline connecting a sub-station with the central office, a

cord circuit at the central office for making' connection with the saidline, a signal receiving electro-magnet associated with said line havingtwo differentially connected windings of different energizingcapacities, a connection to a source of current extending from one sideof said line adapted to complete the circuit through both of saidwindings when the circuit is closed at the sub-station to cause alimited energization only of said. electro-magnet whereby the display ofits signal is effected, switch contacts adapted, when the line isconnected with the cord circuit, to cause a greater flow of -currentthrough one of said energizing windings whereby a greater energizationof said electro-magnet is caused to efface said signal, and meanswhereby the operator may determine the idle or busy condition of atested line.

37. In a telephone exchange system, the combination with a telephoneline connecting a sub-station with the central office, a cord circuit atthe central o'l'lice for making connection with the said line, a signalreceiving electro-magnet associated with said line having twodifferentially connected windings of different energizing capacities, aconnection to a source of current extending from one side of said lineadapted to complete the circuit through both of said windings when thecircuit is closed at the sub-station to cause a limited energizationonly of said electro-magnet whereby the display of its signal iseffected, switch contacts adapted, when the line is connected with thecord circuit, to cause a greater flow of current through one of saidenergizing windings without also passing through the other energizingwinding, whereby a greater energization of said electro-magnet is causedto efface said signal, and a signal controlling electro-magnetassociated with said cord circuit and under the control of thesub-station switch when the telephone line is switched for conversation.

38. In a telephone exchange system, the combination with a telephoneline connecting a sub-station with the central oiiice, a cord circuit atthe central office for making connection with the said line, a signalreceiving electro-magnet associated with said line having twodifferentially connected windings of different energizing capacities, aconnection to a source of current extending from one side of said lineadapted to complete the circuit through both of said windings when thecircuit is closed at the sub-station to cause a limited energizationonly of said electro-magnet whereby the display of its signal iseffected, switch contacts adapted, when the line is connected with thecord circuit, to cause a flow of current through one of said energizingwindings without also passing through the other energizing winding,whereby a greater energization of said electro-magnet is caused toefface said signal, and' means whereby the operator may determine theidle or busy condition of a tested line.

39. In a telephone exchange system, the combination with a telephoneline connecting a sub-station with the central office, a cord circuit atthe central office for making connection with the said line, a signalreceiving electro-magnet associated with said line having twodifferentially connected windings of different energizing capacities, aconnection to a source of current extending from one side of said lineadapted to complete the circuit through both of said windings when thecircuit is closed at the sub-station to cause a limited energizationonly of said electro-magnet whereby the display of its signal iseffected, switch contacts adapted, when the line is connected. with thecord circuit, to cause a greater' flow of current through one of saidenergizing windings whereby a greater energization of saidelectro-magnet is caused to efface said signal, means whereby theoperator may determine the idle or busy condition of a tested line, asignal controlling electro-magnet associated with said cord circuitand-under the control of the sub-station switch when the telephone lineis switched for conversation, a second signal controlling electro-magnetassociated with said cord cirare' cuit and energized over the circuitestablished by the connection of the cord circuit to the telephone line,and a supervisory signal jointly controlled by the said twoelectromagnets.

40. ln a telephone exchange system, the combination. with a telephoneline connecting a sub-station with the central oliice, a cord circuit atthe central otiice for making connection. with the said line, a signalreceiving electro-magnet associated with said line having twodifferentially connected windings of di'ilerent energizing capacities, aconnection to a source of current extending from one side ol" said. lineadapted to complete the circuit through both of said` windings when thecircuit is closed at the sub-station to cause a limited energizationonly ol" said electromagnet whereby the display of its signal iseffected, switch contacts adapted, when the line is connected. with thecord circuit, to cause a greater How of current through one of saidenergizing windings whereby a greater energization of saidelectro-magnet is caused to efface said signal, a signal controllingelectro-magnet associated with said cord circuit and under the contrololZ the sub-station switch when the telephone line is switched forconversation, a second signal controlling electro-magnet associated withsaid. cord circuit and energized over the circuit established by theconnection ot the cord circuit to the telephone line, and a supervisorysignal jointly controlled by the said two electro-magnets.

4l. A telephone system. comprising a telephone line extending from asubstation to a central oHice, a cord-circuit for making connection tosaid line, means for holding conversation over said line andcord-circuit, a call-signal associated with said line at the centralofhce, a controlling electromagnet for said signal having a pluralityol' energizing windings, means under the control of the subscriber lorenergizing said electromagnet by supplying current over a path through aplurality of said windings, means under the control of the operator formodifying the said energization by supplying current through. a lessnumber of said. windings, and means responsive to the initialenergization to display said. signal and to the modified energization toeilace said signal.

42. A telephone system comprising a telephone line extending from asubstation to a central ol'lice, a cord-circuit for making connection tosaid line, means for holding conversation over said line andcord-circuit, a

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call-signal associated with said line at the central ol'lice, acontrolling electromagnet for said signal having a plurality ofenergizing windings, means under the control of the subscriber Aforenergizing said electromagnet by suppling current over a path through aAplurality olisaid windings, means under the control of the operator forincreasing the said energization by supplying current through a lessnumber of said windings, and means responsive to the initialenergization to display said signal and to the increased energization toefface said signal.

43. A telephone system comprising a tele-v phone line extending from asubstation to a central ol'lice, a cord-circuit for making connection tosaid line, means for holding conversation over said line andcord-circuit, a call-signal associated with said line at the centraloliice, a controlling electromagnet for said signal having a pluralityof energizing windings, means under the control of the subscriber 'forenergizing said electromagnet by supplying current ovei' a path througha plurality of said windings, means under the control of the operatorfor modifying the said energization by supplying current to one only ofsaid windings, and means responsive to the initial energization todisplay said signal and to the modified energization to eilace saidsignal and to render certain of the remaining energizing windingsnon-effective.

44. A telephone system comprising a telephone line extending from asubstation to a central oi'hce, a cord-circuit for making connection tosaid line, means for holding conversation over said line andcord-circuit, a call-signal associated with said line at the centralothce, a controlling electromagnet for said signal having a plurality ofenergizing windings, means under the control of the subscriber forenergizing said electromagnet by supplying current over a path through aplurality of said windings, means under the control of the operator formodifying the said energization by supplying current to one only of saidwindings7 and means responsive to the initial energization to displaysaid signal and to the modiilied. energization to e'l'lace said signaland to render all of the remaining energizing windings non-effective.

ln witness whereof, l hereunto subscribe my name this 8th day of OctoberA. D., 1904.

HARRY G. WEBSTER. lditnesses z A. H. DYsoN. CAROLYN WEBER.

